This invention relates to a piston having a defined dry film lubricant coated surface and to a process and apparatus of coating a defined surface of a piston with a dry film lubricant.
It will be appreciated that during operation of an engine having reciprocating engine parts which involve frictionally engaging piston and cylinder members, surface portions of the pistons are exposed to enormous stresses and experience high sliding speeds. These stresses generally result in the wearing of materials and deterioration during the operation of the piston-cylinder devices. It has been proposed heretofore that a wear resistant dry lubricant film be bonded to the piston skirts to protect against these stresses and improve engine efficiency.
To form the dry lubricant film on the piston skirt, heretofore a wetted dispersion of the dry film lubricant has been applied by means of a spraying apparatus using a suitably dilute solution of the film lubricant. Such a method, however, requires that all areas of the piston other than the piston skirt be masked or covered to prevent them from being contacted by the lubricant dispersion. Masking of the pistons is quite time-consuming and, therefore, quite costly. Masking also does not always avoid coating undesirable portions of the piston. In addition, the indiscriminate spraying of the piston with lubricant is wasteful and causes pollution problems. Presently, there are no known methods available for precisely and discriminately applying dry film lubricants to piston skirts. The current spray method for application of dry film lubricants to the friction bearing surfaces of pistons are time-consuming, waste lubricant and cause pollution.